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New exhaust thoughts and possible smog delete

Joel Wilson

Joel Wilson

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Okay, Cali has some strict smog laws but I don't live there anymore. Kentucky has no smog. I need to upgrade my exhaust, dual 2" with a semi built 400 and stock log manifolds just doesn't cut it. Wanting to go up to 2.5" duals, probably glasspacks. Engine has World Products Torquer 2.02 heads with roller rockers, Jegs intake, Qjet, Pertronix ignition, Comp Cams Xtreme energy 4x4 cam, Moroso oil pan with crank scraper, stock pistons and a reconditioned crank. So that being said, I would like to delete the smog pump, EGR valve and the AIR hoses and fittings. Not really to gain power but just to clean up and simplify the engine compartment. Thinking of at least Rams Horn manifolds but I am not against headers if I know they will fit properly, ie. No interference problems. Doug Thorleys would be nice but I have only seen them in the 1k range. I know the Jimmy is not going to be a speed demon but I want it to breathe. What are some decent Rams Horn manifolds? Prices seem to be ultra cheap to 300 ish. So what are some decent headers that are between 300 and 1k? I don't mind spending good money on a set of headers IF they fit right. What is the power gain difference between Rams and Thorleys tri Y's? And why don't they make a homebrew header kit? I know for headers you need thick flange and 14 gauge tubes if possible. Anything else I need to look for in headers?

Thanks, Joel
 
I think rams horns are going to dump in the worst possible place on a squarebody. Right over the engine crossmember. There is a distinct reason why you never see a square running them and that’s it. That puts you in the world of headers and all that it comes with.

Cheap ones fit like crap and don’t last long either. Spending more doesn’t always insure better fit. I’ve had headers on my previous K5 and it was a whack-a-mole type game of chase the exhaust leak. Soft copper gaskets on the flange at the head and collector helped but didn’t solve it.

Yes if you spend more money on a quality name brand it should fit better and last longer but search sound here, no one brand is perfect. Many modify to install v-band clamps at the collector and spend extra money on locking hardware at the flange to the head.

Guys may chime in with header choices but reasearch is your friend on how well they do fit.
 
I got really lucky and bought some Edelbrock TES shorty headers just before they stopped making them. Dead soft aluminum gaskets, never had a problem AFTER messing with the collector area. My other engine was an LS and went log type.

I can’t see figuring this out again. PITA. The Edelbrocks worked great (though I wish the primaries were larger) I don’t know if JBA even makes stuff anymore. :(
 
Hedmans fit. You've got to get the right ones, but there are a couple threads with the exact number. Oddly they are not the ones spec'd for these trucks IIRC, they are not full length and thus don't interfere with the shackles.

I would seriously consider single 3". It's a lot cheaper and easier to run single than duals, especially with headers where the mounting needs to be solid, 3" supports plenty of power, and it's a LOT cleaner under the rig (read: easier to work on stuff).

I used to have leak issues with my headers, the problem is the leverage poorly supported exhaust puts on the headers both at the head and at the collector. I bought OEM exhaust springs to see how those would work with headers at the collector, but I haven't tried them, as it's not gotten loose in years. Since I took the time to properly secure the exhaust rearward of the headers.
 
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I’d get rid of the smog, keep the manifolds and run a nice 3” exhaust, I hate headers, never had a set that didn’t leak.
 

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I've been running ceramic coated long tubes from Summit on my small block for 5 years with no leaks or complaints.
 
Got some video/audio. I can't reduce the video quality, so they are probably going to be big files. Only matters if you have a slow connection, but you can always drop the quality down to 144. All you need is the audio. I took these about 10 ft from the exit. Stock routing, I believe this is a flowmaster 10. It was on my spare rig and I didn't want to buy another muffler, so no idea what it really is. But it's got a small case.

This is it idling in open loop. Definitely a different tone, it doesn't run as clean open loop as it does closed since I haven't spent any time playing with it. I expect a carb tuned properly would likely notice different tone as well.


This is after it goes closed loop. Doesn't really matter except you can hear the idle is different. When the engine RPM gets up there then decelerates the first time, it has hit the rev limit. And no, I'm not a fan of noise. But I think it sounds pretty good when you get on it, if that's the sound you are looking for. It will be getting replaced with a converter and a quietflow muffler at some point. I'll take the lessened interior (and exterior) noise over the minimal loss in power it may make.

 
That sounds really good man. And I'm going to have to think about that, a lot. I think I am going to go with those Hookers that Wes mentioned and then I just need to decide whether duals or 3". Maybe duals with an H pipe. I had a 76 that had an H pipe and it shifted the entire power curve up about 500-750 rpms. It developed some hairline cracks when I was pulling heavy loads and had to start out in granny low a lot. The torque put too much stress in the h pipe so I cut it out and capped it. Torque curve went back to the lower end. And it was noticeable on a stock 350 with 30" glasspacks in a 76 C20. If I could put in a removable H pipe that has some give...
 
I have ran headers on several trucks since 1986. I figured out how a bunch with keeping them sealed up. But they aren't as easy to keep leak free as manifolds.
As @ZooMad75 said, don't try ramhorn style because of the engine mounts.
i also wouldn't mess with any short headers because of how difficult it is to keep the plug wires safe. I had a short set of center dump Sanderson headers give me pure grief with collector leaks and then cracked tubes. Yes, I had flex pipes.
I like long tube headers the best, but they can cause problems at the shackle. Mid length Hedmans are nice, EXCEPT that they run through the same space as the automatic transmission shift linkage. That causes a rework.

I have used both lengths of Hedmans with good results. So far the newer ball and socket collector is nice, just don't use the serrated nuts that they come with, get crimp-lock nuts.

I like having a crossover pipe in dual exhaust anymore, so a single 3" makes sense, but the crossover pipe routing can be a pain, IMO. Not that heat shield installation for the right pipe in duals is easy either.
 
FWIW, here are the headers mocked up with the engine out of the truck. I know I have one with them in the truck, but I apparently didn't upload it here. I'm not running any smog stuff either, though eventually I'm going to run EVAP properly, and a Converter.

full


I had duals, I'll never go back. I would be willing to bet the difference between headers and manifolds offsets any gain from an H-pipe. Pipe sizing is an art, particularly when it comes to scavenging/velocity, which is what we need to make torque. I would imagine duals would need to be 2-2.25" piped to equal a single 3". And even then, surface area will be larger, reducing velocity, which is likely offset by the y-pipe bends in a single setup.

In the grand scheme of things, dialing fuel delivery in is going to make a lot more difference than exhaust, outside of headers which are demonstrably worth easily 10+ HP (and far more torque) on a SBC.
 
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Joel Wilson said:
Okay, Cali has some strict smog laws but I don't live there anymore. Kentucky has no smog. I need to upgrade my exhaust, dual 2" with a semi built 400 and stock log manifolds just doesn't cut it. Wanting to go up to 2.5" duals, probably glasspacks. Engine has World Products Torquer 2.02 heads with roller rockers, Jegs intake, Qjet, Pertronix ignition, Comp Cams Xtreme energy 4x4 cam, Moroso oil pan with crank scraper, stock pistons and a reconditioned crank. So that being said, I would like to delete the smog pump, EGR valve and the AIR hoses and fittings. Not really to gain power but just to clean up and simplify the engine compartment. Thinking of at least Rams Horn manifolds but I am not against headers if I know they will fit properly, ie. No interference problems. Doug Thorleys would be nice but I have only seen them in the 1k range. I know the Jimmy is not going to be a speed demon but I want it to breathe. What are some decent Rams Horn manifolds? Prices seem to be ultra cheap to 300 ish. So what are some decent headers that are between 300 and 1k? I don't mind spending good money on a set of headers IF they fit right. What is the power gain difference between Rams and Thorleys tri Y's? And why don't they make a homebrew header kit? I know for headers you need thick flange and 14 gauge tubes if possible. Anything else I need to look for in headers?

Thanks, Joel
Click to expand...

Joel Wilson said:
Okay, Cali has some strict smog laws but I don't live there anymore. Kentucky has no smog. I need to upgrade my exhaust, dual 2" with a semi built 400 and stock log manifolds just doesn't cut it. Wanting to go up to 2.5" duals, probably glasspacks. Engine has World Products Torquer 2.02 heads with roller rockers, Jegs intake, Qjet, Pertronix ignition, Comp Cams Xtreme energy 4x4 cam, Moroso oil pan with crank scraper, stock pistons and a reconditioned crank. So that being said, I would like to delete the smog pump, EGR valve and the AIR hoses and fittings. Not really to gain power but just to clean up and simplify the engine compartment. Thinking of at least Rams Horn manifolds but I am not against headers if I know they will fit properly, ie. No interference problems. Doug Thorleys would be nice but I have only seen them in the 1k range. I know the Jimmy is not going to be a speed demon but I want it to breathe. What are some decent Rams Horn manifolds? Prices seem to be ultra cheap to 300 ish. So what are some decent headers that are between 300 and 1k? I don't mind spending good money on a set of headers IF they fit right. What is the power gain difference between Rams and Thorleys tri Y's? And why don't they make a homebrew header kit? I know for headers you need thick flange and 14 gauge tubes if possible. Anything else I need to look for in headers?

Thanks, Joel
Click to expand...
My 5.7 has headers, that fit my 76 k5 very nicely. Summit # BIG-11506FLT
there are charts that guide you through choosing pipe size. Idk about the rest of you, but I'm not paying for extra pipe that the engine will never utilize ;)
 
When it comes to headers they do not make much of a power difference over log manifold unless you are running over 4000 RPM a lot. The same with dual exhaust over single exhaust. Dual exhaust with a square body can only really be done well when running both exhaust tubes down the left side. Over at the Fab Rats web site they have a square body that has a well designed dual exhaust set that runs both tubes down the left side.
 
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